The effect of endogenous progesterone on serum levels of 5 alpha-reduced androgens in hirsute women.

This study was to examine indirectly the effect of endogenous progesterone, a known competitor for 5 alpha-reductase, on androgen metabolism in target organs in hirsute women. Serum levels of progesterone, testosterone (T), androstenedione (A), dihydrotestosterone (DHT) and 5 alpha-androstane 3 alpha 17 beta-diol (3 alpha-diol) and sex hormone binding globulin (SHBG) were assessed serially over a four week period in normal women, six hirsute women with regular menstrual cycles, eight hirsute women with oligomenorrhoea (and presumptive polycystic ovaries) and seven non-hirsute women with oligomenorrhoea. Serum T and A levels were significantly higher than normal in both hirsute and non-hirsute women with oligomenorrhoea, while serum SHBG was significantly lower than normal in the two groups of hirsute women. The calculated free T level was higher than normal in all three groups of patients. DHT levels were not significantly different from normal in any of the three groups of patients. The 3 alpha-diol level showed considerable overlap with normal in all groups of patients and was only significantly higher than normal in hirsute women with oligomenorrhoea (P less than 0.05). There was a small fall in DHT in the late luteal phase of the cycle of those women with a sustained rise in serum progesterone in the second half of the cycle, but no change in serum 3 alpha-diol. These studies suggest that serum 3 alpha-diol may not be as good an indicator of peripheral androgen metabolism in hirsute women as previously reported and that a rise in serum progesterone has only a minimal effect on circulating levels of the active 5 alpha-reduced androgen metabolites. Although in vitro 3 alpha-diol has been shown to be a potent inhibitor of 5 alpha-reductase this casts doubt on its role in this regard in vivo.